The present invention is generally directed to generating power, and more particularly to Nano-Electro-Mechanical System (NEMS) power generators including magnetic fluids.
Micro-Electro-Mechanical Systems (MEMS) are miniaturized devices that integrate mechanical and electrical components on a common silicon substrate. Examples of MEMS mechanical devices are motors, pumps, relays, and actuators. MEMS are used in all types of miniaturized technologies from remote sensors and cellular communications to space based electronic systems and phased-array antennas. All of MEMS mechanical and electrical components require power, therefore unconventional, uninterrupted, and portable power sources for miniaturized technologies are in high demand.
Recently, there has been a strong need for NEMS, nanoscale systems of mechanical elements, such as motors, pumps, relays, and actuators and electronics on a common silicon substrate. The advent of NEMS has increased the need for miniaturized and especially nanoscale power generators.
Magnetic fluids are magnetic field responsive fluids containing magnetic particles coated with a surfactant and dispersed in a carrier liquid. Magnetic field responsive fluids provide variable stress levels created by magnetic coupling of the magnetic particles in the form of chains or bent wall-like structures upon interaction with an external magnetic field. Force absorbing devices, such as dampers, shock absorbers, seals, valves, commonly employ magnetic fluids. However, few devices that generate electric power employ magnetic fluids.
Power generators employing magnetic fluids are magnetically driven generators, while most other types of power generators are electrically driven. Magnetically driven generators have two primary advantages over electrically driven generators. First, they are not subject to any catastrophic failures analogous to electrical breakdown, and second, they have a higher energy density (about two orders of magnitude greater). Thus, it is advantageous to have a power generator for a NEMS utilizing a magnetic fluid to produce electricity.
U.S. Pat. No. 4,064,409 discloses a closed ferrofluid circuit surrounded by a magnet. Heating and cooling the ferrofluid takes advantage of the ferrofluid's magnetic properties to pump the ferrofluid through a solenoid and generate electric power. The device disclosed in this patent is thermally driven, while the present invention is directed to a magnetically driven power generator. In the present invention, alternating and traveling magnetic, fields rather than heating and cooling, take advantage of the magnetic fluid's magnetic properties to pump the magnetic fluid through external pickup coils and generate electric power.
U.S. Pat. No. 4,613,304 discloses a hydrogen gas generator system containing permanently magnetically polarized particles in a hydrogen/oxygen collection chamber. An electrical and/or mechanical pump circulates the magnetic particles in a non-magnetic, non-conductive closed loop of tubing. The circulation of the magnetic particles induces a voltage in a coil surrounding the tubing which may be utilized as an electrical power source. This electrical power source is therefore electrically or mechanically driven, while the present invention is magnetically driven.
U.S. Pat. No. 5,714,829 discloses a method for cooling a system having predictable bursts of heat dissipation using an electromagnetic heat engine. The heat engine includes a magnetic medium having susceptibility that varies with temperature and is magnetized between bursts of heat dissipation to create a magnetic field. An electrical load absorbs energy from the magnetic field by demagnetization. Again, the system disclosed in this patent is thermally driven, while the present invention is directed to a magnetically driven power generator.
U.S. Published Patent Application 2001/0033384 discloses the application of an electric or magnetic field on a thin ferrofluid sample to modulate light. The present invention is designed to generate electricity, not modulate light.